I wouldn't suggest you buy a single-family home to live in because the additional cost outweighs the benefits.

Single family house, which required smaller down-payment and little cosmetic repairs.

A lifelong friend and I are motivated to (virtually) meet and connect with those in REI working in the Pittsburgh area.I'm active duty military and living in California with two rental properties (one in Virginia Beach & one in Pittsburgh) and my close friend owns a single family in Baltimore.  

@Khaled El Dorry This strategy is know as a consolidation exchange, and like what @Adam Bartomeo said a single buyer might be difficult to find.

I like both of your ideas so I would look for the single where an ADU is permitted or one with a dump ADU to renovate (that's best) and balance that against the purchase of a 2-4 unit.

The IRS changed how they treat single-member LLCs (solopreneurs like myself) and I expect there will be more changes like in Illinois coming. 

You cannot even apply for an STR permit on a single family home until after you've owned it for five years (and there is no guarantee you will get the permit).

Would it be a bad idea to buy a single family home built in mid 1930's?

Pretty much every small business other than some obscure ones that are excluded (see below) If you have 12 Single Member LLCs that own your rental properties.

When all the dust settles, and the  person searching is tired and discouraged and gives up, Jerry may not have bought  a single lot, but he's made some money from the training he sold you, which was his main goal from the beginning!